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flamp

Sends files over radio in numbered blocks that can be filled in later

What it does

Breaks a file into numbered blocks, each individually checksummed, and transmits them through fldigi. Receivers report which blocks they are missing, and the sender retransmits only those. AMP -- Amateur Multicast Protocol -- is designed so one transmission serves many receivers at once.

Why you would want it

Sending a file over HF means accepting that parts of it will not arrive. Everything else either fails and starts over or needs a two-way connection per receiver, and neither works when twenty stations are copying the same net. This is the mechanism that makes broadcast file transfer over a noisy channel actually work, which is why EMCOMM traffic handling uses it.

Before it will work

fldigi running and configured, since flamp does not own a modem or a radio -- it hands blocks to fldigi and reads what fldigi decodes.

How it installs

  • apt: flamp

Known problems

A receiver that started late gets the blocks from then on and requests the rest; if nobody is transmitting fills, the file simply stays incomplete and nothing announces it. Check the block report rather than assuming a transfer finished. Mode choice matters more than it looks: a mode too fast for conditions loses more blocks than the fill cycle can recover.

Keeping it current

  • probe: apt policy
  • strategy: apt_upgrade

Where to get help with the software itself

The W1HKJ suite, maintained by the fldigi developers. The linuxham group on groups.io is where the answers actually are.

Source: catalog/packages/flamp.yaml